I. Field of the Invention
The present invention relates to a tool holder for a cutting bar in which the radial distance between the axis of rotation of the tool holder and cutting edge of the cutting bar is adjustable and more particularly to such a tool holder in which the bearing sleeve and the biasing means are replaced by members constructed of a compressible material.
II. Description of the Prior Art
There have been many previously known tool holders which are particularly adapted for use in conjunction with cutting bars. Of these, O. R. Briney and J. W. Briney in their U.S. Pat. Nos. 3,125,903 and 2,833,169 disclose cutting tool holders for cutting bars in which the radial distance between the axis of rotation of the holder and the cutting edge of the cutting bar is adjustable.
These previously known tool holders achieve this adjustability feature by means of a bore in the tool holder which is eccentric to the axis of rotation of the tool holder. A cutting bar is secured to a bar holder having a shank which is received within the eccentric bore. Rotation of the bar holder within the eccentric bore thus varies the radial distance between the cutting edge of the cutting bar and the axis of rotation of the tool holder.
Previously a sleeve of ball bearings has been disposed between the eccentric bore and the shank of the bar holder. The ball bearings not only prevent radial movement of the bar holder within the eccentric bore but also permit a smooth rotation of the bar holder within the eccentric bore.
These previously known ball bearing sleeves, however, suffer several disadvantages unknown to the present invention. One disadvantage is that the ball bearing sleeves must be protected from dirt and debris by seal members or the like which require periodic replacement. However, even with the seal members, dirt and debris often reach the ball bearing sleeve which necessitates cleaning and perhaps replacement of the ball bearings. Such maintenance is not only expensive to perform, but also results in down time for the cutting tool holder.
A further disadvantage of the previously known tool holders with ball bearing sleeves is that the initial cost of the ball bearing sleeve is relatively high. Moreover, the ball bearing sleeve eventually wears out and requires an expensive replacement.
A still further disadvantage of these previously known tool holders with ball bearing sleeves is that the ball bearing sleeves are prone to failure. Failure of the ball bearing sleeve during a cutting operation is not only likely to damage the workpiece, but also presents a serious safety hazard for the operator of the cutting machine. Such cutting tool holders have also employed relatively expensive spring members to bias the bar axially as a means of frictionally retaining the tool bar in its adjusted rotated position.